As per BooksOnLine you could use the following query (based on sys.dm_qn_subscriptions DMV)
SELECT qn.id AS query_subscription_id
,it.name AS internal_table_name
,it.object_id AS internal_table_id
FROM sys.internal_tables AS it
JOIN sys.dm_qn_subscriptions AS qn ON it.object_id = qn.object_id
WHERE it.internal_type_desc = 'QUERY_NOTIFICATION';
GO